Recently oxygen concentrators have become used extensively for home care patients. Oxygen therapy using breathable gaseous mixtures containing relatively high oxygen concentrations of between about 80 and about 95% is highly advantageous in treating chronic respiratory or pulmonary ailments. As an alternative to the use of oxygen cylinders which have to be frequently replaced and refilled, oxygen concentrators are more convenient, simple to operate, and economical.
Oxygen concentrators used today are of the type in which atmospheric air is pumped through a molecular sieve bed from which gas nitrogen is adsorbed resulting in a gaseous mixture having substantially increased oxygen concentration. The gas is then delivered usually through a nasal cannula, a patient often requiring the increased oxygen delivery much of the time, if not exclusively. Because most patients require a reasonably specific selected concentration of oxygen in the breathable gaseous mixture, the ability of the apparatus which supplies the oxygen to maintain continuous delivery of the necessary concentrations is important. Where oxygen concentrations fall below selected or required limits, substantial patient injury may result. With oxygen concentrator devices presently used, the oxygen concentration being delivered by the apparatus is unknown to the patient. Thus, the apparatus may malfunction without the user's knowledge, possibly resulting in substantial injury before the malfunction is even realized. Even when the apparatus is provided with alarms, present methods of sensing oxygen in the device is unsatisfactory because of extremely low sensor life. Moreover, when low concentrations are sensed, the apparatus simply becomes useless since specialized technicians are usually required to repair the malfunction before suitable oxygen concentration deliveries can be resumed. It is to the elimination of the aforesaid problems and disadvantages that the improved apparatus of the present invention is directed.